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Q&A on Influenza

インフルエンザ

Q&A on Influenza, FY 2017

As of December 26, 2017

[Overview of Influenza]

Q.1 : What is the difference between Influenza and the common cold?
Q.2 : When will influenza activity begin and when will it peak?
Q.3 : What is the difference between seasonal influenza and novel influenza?
Q.4 : What are the current situations of avian flu A (H7N9) reported in China in 2013?
Q.5 : What is the current situation of the pandemic in 2009?
Q.6 : What types of flu viruses are currently circulating in Japan?
Q.7 : What is the current circulation of influenza in the world?
Q.8 : What is the history of influenza pandemics?

[Prevention and Treatment of Influenza]

Q.9 : What should I do to prevent influenza?
Q.10 : What should I do when I have flu symptoms?
Q.11 : What kinds of influenza antiviral drugs are available?
Q.12 : What is drug-resistant influenza virus?
Q.13 : Are antiviral drug resistant influenza viruses circulating in Japan?
Q.14 : There were some media reports on abnormal behavior including fatal falling incidents after taking influenza antiviral drugs. Is there any causal relationship between taking influenza antiviral drugs and abnormal behaviors?
Q.15 : What should we do for prevention of fatal incidents caused by abnormal behaviors?
Q.16 : Are antibacterial drugs effective for influenza?
Q.17 : How long should I stay inside when I am diagnosed with influenza?

[Influenza Vaccination]

Q.18 : Is one (1) dose of vaccination adequate?
Q.19 : I got vaccinated last year. Should I get vaccinated this year, too?
Q.20 : Please tell me the efficacy and effectiveness of vaccine.
Q.21 : What is the effectiveness of influenza vaccine in infants?
Q.22 : Is it possible that the effectiveness of influenza vaccine declines in the process of production?
Q.23 : What is “quadrivalent vaccine”? For what kind of influenza is this year’s vaccine effective?
Q.24 : When is the best time to be vaccinated for influenza?
Q.25 : Are sufficient vaccine supplies available?
Q.26 : Regarding a product available for multiple doses from the same vial, for how long can a single vial be used?
Q.27 : How much does it cost to get an influenza vaccine?

[Routine vaccination]

Q.28 : Who is eligible for influenza vaccination based on the Immunization Act?
Q.29 : Where can I get the routine vaccination (Please check the description) against influenza based on the Immunization Act? How much does it cost?
Q.30 : Can I always receive routine vaccination against influenza based on the Immunization Act if I am eligible and want to receive it?

[Adverse Events, etc.]

Q.31 : What are the symptoms (adverse events) caused by influenza vaccination?
Q.32 : Are there any fatal cases after influenza vaccination?
Q.33 : Can the influenza vaccination cause influenza?
Q.34 : What responses will be made if serious health damage is caused by influenza vaccine?

[Overview of Influenza]

Q.1: What is the difference between Influenza and the common cold?

(Answer) In general, the common cold is caused by various viruses and most of the common cold symptoms include sore throat, runny nose, sneezing and coughing but general symptoms are rare. With the common cold, fevers are generally not as high as influenza and the symptoms are often less severe.

On the other hand, influenza is an illness caused by infection by an influenza virus. Most common symptoms include a headache, fever of over 38°C, headache, arthralgia and myalgia, and fatigue, and these symptoms usually develop rather rapidly. As in the case of the common cold, sore throat, runny nose and coughing occur as well. Children may have a high risk of acute encephalopathy, and the elderly and those with weak immunity may develop pneumonia.

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Q.2: When will influenza activity begin and when will it peak?

(Answer) Outbreaks of seasonal influenza occur annually, and infection rapidly spreads among many people. In Japan, influenza activity most commonly peaks between December and March.

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Q.3: What is the difference between seasonal influenza and novel influenza?

(Answer) Antigenicity of influenza A viruses undergoes subtle changes every year causing annual outbreaks in humans around the world. This is seasonal influenza.

On the other hand, when a novel influenza virus with dramatically different antigenicity emerges, against which many people have not developed immunity, a nationwide outbreak of novel influenza occurs. It is extremely difficult to predict when and where a novel influenza pandemic will occur. However, once it occurs, it may have a great impact on the life and health of the people, healthcare systems, people’s daily lives, and the entire economy.

Novel pandemic viruses in the past include Spanish Influenza (1918-1919), Asian Influenza (1957-1958), Hong Kong Influenza (1968-1969), Novel Influenza A (H1N1) (2009-2010). As the virus spreads all around the world and many people acquire immunity against the novel influenza virus, it becomes seasonal influenza. H1N1 Influenza (2009) is now treated as seasonal influenza since April 2011.

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Q.4: What are the current situations of avian flu A (H7N9) reported in China in 2013?

(Answer) Many human cases infected with an avian influenza (H7N9) virus were reported in China in April 2013. The number of infected people dropped sharply during the summer of 2013. However, many cases of human infections were reported again between November 2013 and May 2014. Since then, cases of infection have been reported during the winter. The World Health Organization (WHO) has reported 1,564 cases of human infection as of November 2, 2017; in details, there were 1,556 cases in China (Including Hong Kong and Macau), 5 cases in Taiwan. As imported cases from China, one case in Malaysia and two cases in Canada have been reported. Please see the website of the WHO for details of infectious cases.

World Health Organization (WHO): Avian influenza A(H7N9) virus


Although there has been no report yet of human-to-human sustainable transmission, suspected cases of limited human-to-human transmission have been reported. It is therefore necessary to be observed carefully. Please see the website of the Infectious Disease Surveillance Center for more information and the latest risk assessments

National Institute of Infectious Diseases: Influenza A (H7N9)

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Q.5: What is the current situation of the pandemic in 2009?

(Answer) In April 2009, an outbreak of novel strains of influenza A (H1N1) 2009 was reported in Mexico and many people were infected in other parts of the world. Since many Japanese people did not have the immunity against the novel influenza virus, pandemic occurred in Japan in the fall of 2009, affecting approximately 20 million people in a little over a year since the pandemic occurred. About 18,000 people were hospitalized and 203 people died. The death rate was 0.16 (16 per 100000 populations), which remained low compared to other countries. In the following year, in addition to the novel influenza A (H1N1) virus, Hong Kong flu A and flu B became nationally noticeable. No special situations of pandemic at different times from seasonal influenza have been confirmed.

In the light of this circumstances, the Ministry of Health, Labour and Welfare of Japan (MHLW) decided to treat the influenza A (H1N1) 2009 viruses, which had been called the “novel influenza” at the time of March 31, 2011, as a seasonal influenza and shifted the measures to the measures against seasonal influenza.

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Q.6: What types of flu viruses are currently circulating in Japan?

(Answer) There are three main types of influenza: A, B and C, of which influenza A and B cause circulate annually as one of the seasonal flu.

The types of flu viruses circulating in Japan in recent years are A (H1N1) , A (H3N2) (Hong Kong Flu), and B. The influenza virus A (H1N1) subtype caused a pandemic in 2009 (H1N1pdm). Influenza virus A (H1N1) that had been circulating as seasonal influenza before 2009, referred to as the “Russian flu”, practically disappeared following the A (H1N1) 2009.

These three types of influenza viruses circulate worldwide every year but the types or subtypes of circulating viruses differ by country or region, and by year. The details of influenza viruses in circulation are available on the website of the Infectious Disease Surveillance Center.

National Institute of Infectious Diseases Influenza Surveillance Center: What is the Influenza?

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Q.7: What is the current circulation of influenza in the world?

(Answer) Although the timing is different by region, influenza occurs around the world. In general, the peak period of influenza is during the winter in the temperate regions (June-September in the Southern Hemisphere). The peak period in the tropical and subtropical areas varies by country and region, and there are regions with a low level of influenza activity throughout the year and there are regions with several peak periods. The types of viruses in circulation may differ by region, but not greatly. The website of the WHO provides information on influenza activity.

WHO: Influenza updates

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Q.8: What is the history of influenza pandemics?

(Answer) Recorded pandemic influenza has a long history, but the scientifically proven presence of influenza dates back to around 1900. In addition to annual circulation, several global epidemics have been documented.

In particular, “Spanish Flu (caused by A(H1N1) virus)” is said to have killed 20 million to 40 million people worldwide and 0.4 million in Japan.

Later, the world was hit by the “Asian Influenza A(H2N2) ” in 1957, “Hong Kong Influenza A(H3N2) ” in 1968 and “Influenza (H1N1) 2009”.

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[Prevention and Treatment of Influenza]

Q.9: What should I do to prevent influenza?

(Answer) The following methods are effective to protect yourself from influenza:

1) Vaccination before influenza season sets in.

It has been reported that influenza vaccination can reduce the risk of disease onset even if one is infected with influenza and can be effective in making the illness milder if one does get sick. The number of people getting the flu shot is on an increasing trend in Japan.

Please see [Influenza Vaccination]


2) Practicing “cough etiquette” as a protection against droplet infections.

The main route of transmission of influenza is droplet transmission from coughing or sneezing. Therefore, you can greatly reduce the risk of infection by avoiding exposure to droplets.

However, it is easier said than done. It is not easy to prevent droplet transmission because we live in a world where we have close contact with families, friends, and communities. Even if infected with influenza virus, not everyone infected with the influenza virus necessarily develops high fever or respiratory symptoms and is diagnosed with influenza.

There are cases that an infected person does not have any symptoms or he/she and people around him/her do not suspect influenza infection because the symptoms are as mild as a common cold. Therefore, the following actions are important to prevent droplet transmission:

(1) Practice “cough etiquette” and do not cough or sneeze on anyone,
(2) Wear a mask when coughing or sneezing. When there is no mask, cover your mouth and nose with a tissue or sneeze into your upper arm and do not turn your face to others, and
(3) Discard the used tissue into a trash can. Wash your hands immediately when you cough or sneeze into your hands, etc.

Masks are important to prevent droplet transmission. Especially, wearing a mask is highly effective to reduce the spread of influenza viruses when worn by infected patients.

3) Hand washing after coming home from outside, etc.

Washing hands is an effective way to physically remove flu viruses from the skin, such as hands and fingers, and is the basis of preventing any infections, not just influenza, whose transmission routes are by contact or through the droplets. Since alcohol is also effective as a disinfectant against influenza viruses, use of alcohol-based hand sanitizer can be effective.

4) Maintaining appropriate humidity levels.

Dry air lowers the defense function of the respiratory membrane, making us more susceptible to the influenza virus. It is effective to maintain an appropriate humidity level (50-60%) by using a humidifier, especially in a room where the air loses moisture easily.

5) Sufficient rest and balanced diet.

A balanced, healthy diet and sufficient rest daily will help to strengthen the body resistance.

6) Avoiding crowds and busy streets.

When increased number of influenza is reported, you need to avoid crowds and busy streets. This is especially true for elderly persons, anyone with underlying medical problems, pregnant women, and those who feel fatigue and who do not have sufficient sleep. If going out into crowds is not inevitable, one of the protective methods is to wear a sanitary non-woven fabric mask. Nonetheless, it is recommended to try to shorten the time in crowds as much as possible.

*What is a sanitary non-woven fabric mask?
“Non-woven” fabric is a fabric-like material bonded together by heat or chemical treatment, instead of weaving fibers or yarns. A mask made with such fabric is called a “non-woven fabric mask.

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Q.10: What should I do when I have flu symptoms?
(Answer)
  1. (1) If you start feeling sick, go to see the doctor at an early stage.
  2. (2) You need to have a good rest. Getting enough sleep is particularly important.
  3. (3) Drink plenty of water. You can drink whatever you like; soups and teas are also good.
  4. (4) Wear a non-woven fabric mask to avoid transmitting viruses to others when you have coughing and sneezing.
  5. (5) Avoid going out into crowds or busy streets and do not force yourself to go to school or work.

Some abnormal behaviors have been reported in children and young people with influenza, such as suddenly running away, trying to come out of the room or wandering around. It is therefore important to keep an eye on the small children or young patients when they are resting at home for at least two days after the onset of the disease (see Q15).

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Q.11: What kinds of influenza antiviral drugs are available?

(Answer) Antiviral drugs against influenza infection are listed below.

  • Oseltamivir phosphate (trade name: Tamiflu)
  • Zanamivir (trade name: Relenza)
  • Peramivir (trade name: Rapiacta)
  • Laninamivir octanoate (trade name: Inavir)
  • Amantadine hydrochloride (trade name: Symmetrel) (effective only for influenza A)

It must be noted that the effectiveness of these drugs varies depending on the timing of treatment and severity of symptoms. Therefore, the doctor shall decide whether or not to use a medication.

When treatment of influenza with antiviral drugs is given at an appropriate timing (within 48 hours of illness onset), it can shorten the duration of fever by one to two day(s) and reduce the amount of virus excreted from the nose and pharynx. No significant effectiveness can be expected when treatment starts after two days (48 hours) of symptom(s) onset. It is therefore crucial to comply with the dosage regimen and duration (duration of intake) for effective use.

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Q.12: What is drug-resistant influenza virus?

(Answer) Drug-resistant influenza virus is a strain of virus that antiviral drugs are no longer effective or less effective. The drug-resistant virus is thought to emerge through the process of replications during which a change in the genetic mutation occurs.

Drug-resistant influenza virus exhibits resistance to originally effective antiviral drugs; however, a drug-resistant virus with a stronger pathogenicity and infectivity compared to other influenza viruses has not been reported. A drug-resistant influenza virus does not affect the effectiveness of the vaccines.

In Japan, in cooperation with the WHO, the National Institute of Infectious Diseases conducts surveillance of drug-resistant strains. As of the time of writing, it has been confirmed that the emergence rate of oseltamivir-resistant virus in influenza (H1N1) 2009 is low and treatment with Zanamivir or Laninamivir against the separated resistant strains is effective (see the website of the National Institute of Infectious Diseases). Japan will continue watching closely the emergence of the drug-resistant viruses through the monitoring activities.

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Q.13: Are antiviral drug resistant influenza viruses circulating in Japan?

(Answer) In Japan, the National Institute of Infectious Diseases and regional health institutes carry out studies on viruses with resistance to antiviral drugs, such as Tamiflu and Relenza, every year. Please see the website of the National Institute of Infectious Diseases for details.

National Institute of Infectious Diseases: Antiviral Resistance Surveillance in Japan

The detection rate of antiviral drug-resistant influenza viruses is 1% to 4%. Most of these detected viruses are collected after treatment with antiviral drugs.

Viral strains resistant to Tamiflu were detected from the patients who had not been treated with Tamiflu in Sapporo at the beginning of the 2013-2014 influenza season. It has been determined that there was no patient-patient contact. However, since the genetic characteristics of the viruses are very much alike, it is highly possible that the viruses with resistance to Tamiflu co-circulated inSapporo.

In general, viruses with resistance to antiviral drugs spread slowly, do not circulate widely, and fade out naturally. (Detailed information is available at the National Institute of Infectious Diseases).

The National Institute of Infectious Diseases: IASR (Newsletter) Antiviral Drug-resistant Influenza A (H1N1)pdm09 Viruses Detected in Sapporo During 2013-2014 Season

Nonetheless, it is necessary to be vigilant since Tamiflu-resistant Soviet A (H1N1) virus that emerged in Europe spread worldwide during the 2008-2009 flu season.

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Q.14: There were some media reports on abnormal behavior including fatal falling incidents after taking influenza antiviral drugs. Is there any causal relationship between taking influenza antiviral drugs and abnormal behaviors?

(Answer) Some abnormal behaviors (for example, suddenly running away, trying to jump out of a room, wandering around, etc.) after taking influenza antiviral drugs have been reported. In addition, although it is very rare, even cases of death due to falling have been reported as a result of these abnormal behaviors.
* Eight cases of death have been reported since April 2009 (as of the end of August 2017).

It is not clear whether taking influenza antiviral drugs caused these abnormal behaviors. However, the following facts have been reported based on the results of recent research:
・ In some patients with influenza infection, similar abnormal behaviors may appear if no drugs are taken;
・ Abnormal behaviors may appear regardless of the type of influenza antiviral drugs.

For the above-mentioned reasons, careful attention is required for abnormal behaviors when a person gets influenza, regardless of the type of influenza antiviral drug taken or whether a drug was taken or not (see Q15 for specific precautions).

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Q.15: What should we do for prevention of fatal incidents caused by abnormal behaviors?

(Answer) In some patients who have influenza infection, abnormal behaviors have been reported regardless of the type of influenza antiviral drug taken or whether a drug was taken or not (see Q14).

When infants and adolescents get influenza and recuperate at home the guardian should never leave them alone at least for the first 2 days after the diagnosis of influenza, regardless of the type of influenza antiviral drug taken or whether a drug is taken or not,. In addition, in case of the occurrence of abnormal behaviors, the following measures are recommended to prevent the patients from easily jumping out of the home, for example:


(1) In case of a high-rise home
・ Be sure to lock the entrance door and windows of all rooms (including internal and auxiliary locks if any);
・ Let the patient sleep in a room that doesn’t have a balcony;
・ Let the patient sleep in a room with barred windows (if there is a room with barred windows).


(2) In case of free-standing housing
・ In addition to the items in (1), let the patient sleep in a room on the ground floor as far as possible.


○Examples of abnormal behavior
・Suddenly stand up and try to bolt form the room.
・Get in a state of extreme excitement, run around the room with hands wide open and mumbling.
・Try to open the window and go out on a balcony in an excited state.
・Go out of the house and wander around and do not respond to attempted conversation.
・Go outside sensing that someone might attack.
・Start saying something strange, wander around the room crying.
・Burst into laughter and try to run up the stairs.

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Q.16: Are antibacterial drugs effective for influenza?

(Answer) Antibacterial drugs are not effective for influenza viruses, but elderly persons and physically weak persons are especially prone to bacterial infections such as pneumococci. Thus, in some cases, antibacterial drugs are administered as a treatment of complications caused by combined infections with bacteria and viruses, including bronchitis, pneumonia, etc.

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Q.17: How long should I stay inside when I am diagnosed with influenza?

(Answer) In general, it is believed influenza viruses are released in nasal and pharynx secretions for about three to seven days after the disease onset. So it is necessary to avoid going outside during this period.

Although the amount of viruses released decreases as the fever abates, viruses are still released even after the fever subsides. The duration of viral shedding varies among individuals, but while symptoms, such as coughing and sneezing, persist, it is advisable to take sufficient care not to pass on the flu to others by wearing a non-woven mask, etc.

For your reference, the School Health and Safety Act (Act No. 56 of 1958) defines the period of exclusion from school attendance of influenza as “five days after onset of the disease and two days (three days for infants) after defervescence (however, this does not apply if a school doctor or any other doctor confirms there is no risk of infection).

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[Influenza Vaccination]

Q.18: Is one (1) dose of vaccination adequate?

(Answer)

  1. (1)In principle, one (1) dose of vaccination is given for people aged 13 years and older. (Note 1). Although it is stated to use “one or two doses for people aged 13 years and older” in the package insert of influenza vaccines, it is reported that one dose of 0.5 mL influenza vaccine achieves an increase in antibody titer equivalent to two doses of vaccine (Note 2) based on research in healthy adults and people with underlying diseases (chronic diseases) *1, 2. However, for people with some medical reasons who a physician judged, two doses options are available. t (Note 1). Note that one dose is given as the regular vaccination (Note 3).
  2. (2)Two (2) doses are given for people aged 13 years and younger. Since a higher increase in the antibody titer is obtained after two doses of vaccination than after one dose, the following amount and time of doses for influenza vaccine are specified in Japan. Note that people aged 12 years at the first dose and aged 13 years at the second dose can be considered as 12 years old in the following category and have the second dose.
    • (i) People aged 6 months and older to under 3 years: 2 doses of 0.25 mL/dose (Note 4)
    • (ii) People aged 3 years and older to under 13 years: 2 doses of 0.5 mL/dose
  3. (3)Regarding the situation in other countries, the World Health Organization (WHO) presents the view that “a single dose of the vaccine” is appropriate for schoolchildren aged 9 years and over and for healthy adults as the dosage of influenza vaccines (limited to inactivated vaccines). In addition, the Advisory Committee on Immunization Practices in the United States (US-ACIP) recommends that all persons aged 9 years and older (other than “children aged 6 months to 8 years”) should take “1 dose” of influenza vaccine.
  1. (Note 1) People aged 13 years and older with underlying diseases (chronic diseases) who are considered to have significant immunosuppressive conditions may be required to receive 2 doses at the physician’s discretion.
  2. (Note 2) An antibody titer is the amount of antibody that can react with an antigen and the value is obtained by measuring the amount of antibody produced in the human body against viral infection or vaccination.
  3. (Note 3) For eligible persons for regular influenza vaccination, see Q28.
  4. (Note 4) Regarding item (2) (i) above, the condition of “Children aged 1 year and older to under 3 years: 2 doses of 0.25 mL/dose” is applied for some vaccines.
  1. *1. “Analytical Epidemiology Research on the Effectiveness and Safety of Vaccines for Vaccination” (Chief Research Officer: Yoshio Hirota (Osaka City University), the Health and Labor Sciences Research Grant on Emerging and Re-emerging Infectious Diseases from the Japanese Ministry of Health, Labour and Welfare, FY2011
  2. *2. “Analytical Epidemiology Research on Assessment of the Effectiveness and Safety of Vaccine and Application of Measures for VPD (vaccine preventable diseases),” (Chief Research Officer: Yoshio Hirota (College of Healthcare Management)), the Health and Labour Sciences Research Grant on Emerging and Re-emerging Infectious Diseases and Immunization Policy Promotion of the Japanese Ministry of Health, Labor and Welfare, FY2016.

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Q.19 I got vaccinated last year. Should I get vaccinated this year, too?

(Answer) Influenza vaccines are manufactured based on the viruses that are considered to be the most common during the upcoming season. Therefore, it is recommended that people who had an influenza vaccination the previous year also receive an influenza vaccination in the present year.

Q.20: Please tell me the efficacy and effectiveness of vaccine.

(Answer) When a person gets influenza, it begins by the influenza virus entering the body through the mucosal membranes of the mouth, nose or eyes. The virus enters the body, invades a cell and replicates. This condition is referred to as “infection,” and the vaccines have limited effectiveness to completely prevent the course of infection.
When the viruses increase, symptoms of influenza such as fever and sore throat appear after a few days of incubation period. This condition is referred to as “onset of disease.” A certain degree of effectiveness to prevent this “onset of disease” is confirmed with influenza vaccines, but the effectiveness cannot be expected to be as high as those seen with measles and rubella vaccines. After the onset of influenza, many people recover within approximately one week, but some people may have severe complications such as pneumonia or encephalopathy, leading to hospitalization or death. This is referred to as “aggravation” of influenza. People with underlying diseases and elderly people are at an increased risk of aggravation. The most important effect of influenza vaccines is to prevent this “aggravation.”
A study conducted in Japan showed that vaccination effectively prevented the onset of influenza by 34-55% and deaths by 82% among elderly people aged 65 years and older living in nursing homes *1.

The “effectiveness of influenza vaccines” is indicated by an index that shows “how much the risk of getting influenza is reduced in vaccinated people relative to the risk in the unvaccinated people,” based on human subject research. It is reported that the influenza vaccine was effective in preventing the onset by 60% in a study conducted during the 2015/16 season among children under 6 years old *2. The “effectiveness in preventing the onset of influenza by 60%” is equivalent to the following condition:

  • ・ Assuming that 30 of 100 unvaccinated people develop influenza (attack rate is 30%),
  • ・ and 24 of 200 vaccinated people develop influenza (attack rate is 12%),

→ Vaccine effectiveness ={(30 - 12)/ 30}x 100 = (1 - 0.4) x 100 = 60%

The attack rate in vaccinated people is reduced by 60% relative to the rate in unvaccinated people. This means that 60% of those who develop influenza among unvaccinated people (18 of 30 people in the above scenario) could have avoided the onset of influenza if they had been vaccinated.
Current influenza vaccines do not ensure that people never develop influenza if they receive the vaccination. However, the vaccine is considered to have a certain degree of effectiveness in preventing the onset of influenza as well as aggravation and death after the onset of disease.

  1. *1. “Research on the Effectiveness of Influenza Vaccine” (Chief Research Officer: Hitoshi Kamiya (National Mie Hospital), supported by the Health and Labour Sciences Research Grant for Research on Emerging and Re-emerging Infectious Diseases of the Japanese Ministry of Health, Labour and Welfare, FY1999
  2. *2. “Analytical Epidemiological Research on Assessment of the Effectiveness and Safety of the Vaccine and Application of Measures for VPD (vaccine preventable diseases)”, (Chief Research Officer: Yoshio Hirota (College of Healthcare Management)), supported by a Health and Labour Sciences Research Grant for Research on Emerging and Re-emerging Infectious Diseases and Immunization Policy Promotion of the Japanese Ministry of Health, Labour and Welfare, FY2016.

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Q.21: What is the effectiveness of influenza vaccine in infants?

(Answer) Inactivated influenza vaccines used currently in Japan do not have the ability to prevent infection completely, but are effective in some ways to prevent onset of influenza and aggravation of or death from Influenza.

As for the effectiveness of influenza vaccine in infants, the vaccine generally has effectiveness of 20-60% in preventing onset, although it varies depending on reports.* There are some reports indicating effectiveness relating to preventing severity of influenza in infants. (Source: Katayose et al. Vaccine. 2011 Feb 17;29(9):1844-9)

In order to protect infants from influenza virus infections, it is advisable for families and adults around infants to try to reduce chances of infants to be exposed to influenza viruses as much as possible by strictly practicing hand washing and cough etiquette, as well as by avoiding places where a lot of people gather during the peak period.


  1. *1.“Research on Effectiveness of Influenza Vaccine in Infants” (Chief Research Officer: Hitoshi Kamiya (National Mie Hospital) and Masaro Kaji (Kurume University), the Health and Labor Sciences Research Grant on Emerging and Re-emerging Infectious Diseases from the Japanese Ministry of Health, Labor and Welfare, FY2002
  2. *2. “Analytical Epidemiology Research on Assessment of Effectiveness and Safety of Vaccine and Application of Measures for VPD (vaccine preventable diseases)”, (Chief Research Officer: Yoshio Hirota (College of Healthcare Management)), the Health and Labor Sciences Research Grant on Emerging and Re-emerging Infectious Diseases and Immunization Policy Promotion from the Japanese Ministry of Health, Labor and Welfare, FY2016.

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Q.22: Is it possible that the effectiveness of influenza vaccine declines in the process of production?

(Answer) Influenza vaccines are manufactured using embryonated eggs. Egg-adaptation is necessary so that viruses can easily grow in an egg. The egg-adaptation is a process whereby a virus adapts to the environment in the egg through successive cultivation. However, there are cases of genetic mutation of viruses during adaptation. When any genetic mutation occurs, the difference in the degree of the effects on immunity (difference in antigenicity) may be observed between the actual epidemic influenza virus (epidemic strain) and the influenza virus used for vaccine development (vaccine strain). However, even in such cases, epidemiological research shows that a certain degree of effectiveness is maintained for humans. It may be because humans have a certain amount of antibodies due to yearly exposure to the viruses unlike the experimental animals used for the research on influenza viruses.

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Q.23: What is “quadrivalent vaccine”? For what kind of influenza is this year’s vaccine effective?

(Answer) The Influenza vaccine now broadly used in Japan is called “quadrivalent vaccine,” because the vaccine is manufactured by incubating each of the influenza A viruses (H1N1 and H3N2 strains) and influenza B viruses (Yamagata- and Victoria-lineage).

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Q.24: When is the best time to be vaccinated for influenza?

(Answer) The influenza season in Japan is generally between December and April every year and it peaks in late January and early March. Therefore, it is desirable to receive vaccination before mid-December yearly. Regarding this fiscal year, since the start of manufacturing of the vaccine for H3N2 subtype viruses was delayed compared to previous years, the influenza vaccine can be newly supplied after mid-December. If people cannot be vaccinated before mid-December, they may continue to have opportunities to receive vaccination (Note).

  • (Note) The period when regular vaccinations are given depends on the municipality, so please ask at your municipal offices about the period of regular vaccinations.

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Q.25: Are sufficient vaccine supplies available?

(Answer) With the following measures in place, it is expected that almost the same amount of vaccine is secured as in the previous fiscal year (Note 1).

  • Make sure that people aged 13 years and older should receive 1 dose unless physicians recognize the special needs (Note 2) (Note 3)
  • Keep everyone informed that the vaccines should be used more efficiently than the previous year (Don’t order the vaccine unnecessarily early or in unnecessarily large amounts, etc.)
  1. (Note 1) The expected amount of supply this season (as of October 2017) is approximately 52,690 thousand doses (approximately 26,340 thousand vials). The estimated used amount in last year was approximately 26,420 thousand vials. Note that 1 dose is equivalent to the amount of vaccine for 1 healthy adult.
  2. (Note 2) People aged 13 years and older with underlying diseases (chronic diseases) who are considered to have significant immunosuppression may have to receive 2 doses at the physician’s discretion.
  3. (Note 3) See Q18 too.

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Q.26: Regarding a product available for multiple doses from the same vial, for how long can a single vial be used?

(Answer) There are some influenza vaccine formulations with enough medicinal solution filled in one vial for multiple doses. Regarding this type of product, it is described in the package insert that once a vial is opened, the content of the vial should be used within the same day. Please pay attention to the expiration date of the product and the precautions for vaccines, and use within 24 hours from the time of the first access to withdraw fluid.

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Q.27: How much does it cost to get an influenza vaccine?

(Answer) The National Health Insurance does not cover influenza vaccination because it is not treatment for diseases. In principle, you must pay all the fees and the cost is different in each medical institution.

However, the medical expenses may be paid by the public system if a person is eligible for the routine vaccination based on the Immunization Act (Law Number 68 of 1948)(Please double check it out the description). Please ask about it at your local office (health center), medical association, hospital, or your family doctor (some local governments provide original support schemes for those who are not eligible for routine vaccination).

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[Routine vaccination]

Q.28: Who is eligible for influenza vaccination based on the Immunization Act?

(Answer) Those persons categorized below are eligible for routine vaccination(Please check the description) because they are thought to be more severe of influenza once infection occurs and benefit greatly from vaccination. If you are thinking about to receive the flu vaccine, please make a decision upon consultation with your doctor.

(1) People aged 65 or over.
(2) People aged 60-64 with dysfunctions of the heart, kidney, or respiratory organs and are also restricted in daily activities (roughly equivalent to the physical disability level 1).
(3) People aged 60-64 with immune system disorders due to human immunodeficiency virus infection and are also not able to lead a normal life (roughly equivalent to the physical disability level 1).

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Q.29: Where can I get the routine vaccination (Please check the description) against influenza based on the Immunization Act? How much does it cost?

(Answer) You can receive the influenza vaccine(s) at a local medical institution or at a family doctor’s office and the cost and immunization period vary depending on municipality. Please contact the municipal office of your residence (health center), medical association, medical institutions or your family doctor, etc. for schemes of medical institutions and local governments that provide influenza vaccines.

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Q.30: Can I always receive routine vaccination against influenza based on the Immunization Act if I am eligible and want to receive it?

(Answer) You are not guaranteed to be able to receive routine vaccination against influenza anytime you want. A person falling under any of the following items may not be suitable for immunization or must take due care when receiving a vaccine.

Those who are not suitable for vaccination: (Implementation Regulations on Immunization: Ordinance of the Ministry of Health and Welfare No. 27, September 17, 1958. (Latest revision: Ordinance of the Ministry of Health, Labour and Welfare No. 50, March 30, 2013))

  • Persons with fever,
  • Persons presenting with acute serious disease,
  • Persons with a history of anaphylaxis due to the vaccine components, and
  • Any other persons who are not in a suitable condition to receive flu shot(s).

In addition, persons with a past history of fever within two days of influenza vaccination or those who have developed allergy-like symptoms, such as systematic eruptions and who intend to receive flu shot fall into those who are not suitable for vaccination.

Persons requiring precautions when making vaccination decisions
(Implementation Guidelines for routine immunization: “Implementing Immunizations based on the provisions of Article 5, paragraph 1 of the Immunization Act” (Notice of the Director of Health Bureau, Ministry of Health, Labour and Welfare No. 2, Issuance Number 0330 of Health Bureau March 30, 2013 [Annex]).(Please check the descriptions)

  • (A)Persons with underlying diseases, such as cardiovascular diseases, renal diseases, hepatic diseases, hematological diseases, or development disorders, etc. ,
  • (B)Persons with history of convulsion(s),
  • (C)Persons who have been diagnosed as having immunodeficiency, and persons whose close relatives are diagnosed as having congenital immunodeficiency, and
  • (D)Persons who may be at risk of allergic reactions to vaccine components.

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[Adverse Events, etc.]

Q.31: What are the symptoms (adverse events) caused by influenza vaccination?

(Answer) Influenza vaccine is given to produce immunity, but sometimes it can also produce other reactions. This is called adverse events. Rather common adverse events caused by seasonal influenza vaccine include reddening of the skin (rubefaction), swelling (tumefaction), and pain (ache) around the infected area (local). About 10-20% of vaccinated persons develop such reactions but they normally disappear within two to three days.

As for systematic reactions, fever, headache, ague (chill) and fatigue (tiredness) may occur, but they also last only for two to three days.

Although rarely seen, shock and anaphylactic symptoms (rashes, hives, reddening of the skin, itching and breathing difficulties) may occur. The shock and anaphylactic symptoms are allergic reactions to vaccines, which occur relatively soon after the injection. Thus, it is recommended to rest for about 30 minutes after vaccination at the hospital. Please contact the doctor immediately if you experience any of such reactions after coming back to home.

Some cases of serious adverse events (*) have infrequently been reported. It is not, however, clear whether they are definitely associated with the vaccination. The government shall assess the cases of adverse events after influenza vaccination and disclose the results as they become available.
*Guillain-Barre syndrome, acute encephalopathy, acute disseminated encephalomyelitis, seizure, liver dysfunction, asthma attack, and thrombocytopenic purpura have been reported as serious adverse events.

Table. Symptoms that physicians are obliged to report as suspected cases of adverse events after influenza vaccination and the time lapse from vaccination to the onset of the symptoms

Influenza 1. Anaphylaxis
2. Acute disseminated encephalomyelitis (ADEM)
3. Encephalitis / Encephalopathy
4. Seizures
5. Myelitis
6. Guillain-Barre syndrome
7. Optic neuritis
8. Thrombocytopenic purpura
9. Vasculitis
10. Liver dysfunction
11. Nephrotic syndrome
12. Asthma attack
13. Interstitial pneumonia
14. Mucocutaneous ocular syndrome
15. Other reactions
4 hours
28 days
28 days
7 days
28 days
28 days
28 days
28 days
28 days
28 days
28 days
24 hours
28 days
28 days

(Extract from the report on suspected cases of adverse events after vaccination)

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Q.32: Are there any fatal cases after influenza vaccination?

(Answer) In the report on suspected cases of adverse events after influenza vaccination, the cases of death reported by physicians as suspected to be due to the vaccinations are as follows:

Type Period No. of cases
New October 2009 – September 2010 3 cases
October 2010 – March 2011 4 cases
Seasonal October 2011 – May 21 2012 0 case
October 2012 – May 14 2013 1 case
October 2013 – July 2014 1 case
October 2014 – June 2015 3 cases
October 2015 – April 2016 1 case
October 2016 – April 2017 2 case

At the Working Group on Adverse events, experts conducted assessments on these reported cases of adverse events and no direct and clear causal relationship was evidenced between deaths and vaccination. Most of the fatal cases are elderly persons with underlying diseases.
Documents are listed in the following address of the website of MHLW.

Those who have underlying diseases may be adversely affected by various external factors. It is therefore important to ask for advice from your family doctor or a doctor of highly specialized medical institution concerning whether or not vaccination is appropriate and make an appropriate decision.

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Q.33: Can the influenza vaccination cause influenza?

(Answer) No. The influenza vaccination is inactivated. Inactivated vaccine is produced by extracting essential components for immune development, after live pathogenic viruses are inactivated, thereby completely removing pathogenicity. Therefore, the inactivated vaccines cannot cause influenza infection.

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Q.34: What responses will be made if serious health damage is caused by influenza vaccine?

(Answer) If a person falls in the category of immunization described as in the answer section of Q28 and is eligible for routine vaccination under the Immunization Act and when the Minister of Health, Labour and Welfare certifies the health damage has been caused by vaccination, he/she shall be eligible for remediation under the Immunization Act.

Please see the following address for the details of the remedial program.
Remedial Measures for Health Problems Caused by Preventive Vaccination

As for voluntary vaccination not based on the periodical immunization(Please check the description) under the Immunization Act, when a person develops health problems due to adverse events even the vaccine was used properly, the person is eligible either for the Relief System for Sufferers from Adverse Drug Reactions(check the description) or the Relief System for Infections Derived from Biological Products(check the descption) based on the Pharmaceuticals and Medical Devices Agency Law (Law No. 192 of 2002).

Please see the following or contact the Pharmaceuticals and Medical Devices Agency (phone: 0120-149-931) for the details of the relief systems.

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The Ministry of Health, Labour and Welfare (MHLW) has established the “Consultation Desk for Infectious Diseases/Preventive Vaccination” in order to accurately respond to the questions of the people regarding general preventive methods and current state of infectious diseases, including influenza, and significance, effectiveness and adverse events of preventive vaccines, etc.
[Consultation Desk for Infectious Diseases/Preventive Vaccination]
Telephone: 0422-70-1485(from 9 a.m. to 5 p.m. *excluding Saturday, Sunday, holidays & year-end and New year holidays)

* We do not respond to opinions/questions regarding the government.
*The Ministry of Health, Labour and Welfare has assigned an external private company to provide the services of the consultation desk.

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